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          python基础知识(三十二)
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        <h2 id="套接字socket"><a href="#套接字socket" class="headerlink" title="套接字socket"></a>套接字socket</h2><blockquote>
<p>套接字起源于 20 世纪 70 年代加利福尼亚大学伯克利分校版本的 Unix,即人们所说的 BSD Unix。 因此,有时人们也把套接字称为“伯克利套接字”或“BSD 套接字”。一开始,套接字被设计用在同 一台主机上多个应用程序之间的通讯。这也被称进程间通讯或IPC。</p>
</blockquote>
<h3 id="socket模块"><a href="#socket模块" class="headerlink" title="socket模块"></a>socket模块</h3><a id="more"></a>

<p><a href="https://docs.python.org/zh-cn/3/library/socket.html" target="_blank" rel="noopener"><code>socket</code></a>模块提供了访问 BSD套接字的接口</p>
<h4 id="创建套接字"><a href="#创建套接字" class="headerlink" title="创建套接字"></a>创建套接字</h4><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> socket</span><br><span class="line">s = socket.socket()</span><br></pre></td></tr></table></figure>

<h5 id="参数"><a href="#参数" class="headerlink" title="参数"></a>参数</h5><ul>
<li>AF_INET 面向网络的套接字（默认种族）</li>
<li>AF_UNIX 基于文件的套接字</li>
<li>TCP套接字的名SOCK_STREAM（默认类型）</li>
<li>UDP套接字的名SOCK_DGRAM</li>
</ul>
<table>
<thead>
<tr>
<th>常用方法</th>
<th></th>
</tr>
</thead>
<tbody><tr>
<td><code>s.bind()</code></td>
<td>绑定(主机,端口号)到套接字</td>
</tr>
<tr>
<td><code>s.listen()</code></td>
<td>开始TCP监听</td>
</tr>
<tr>
<td><code>s.accept()</code></td>
<td>被动接受TCP客户的连接,(阻塞式)等待连接的到来</td>
</tr>
<tr>
<td><code>s.connect()</code></td>
<td>主动初始化TCP服务器连接</td>
</tr>
<tr>
<td><code>s.connect_ex()</code></td>
<td><code>connect()</code>函数的扩展版本,出错时返回出错码,而不是抛出异常</td>
</tr>
<tr>
<td><code>s.recv()</code></td>
<td>#接收TCP数据</td>
</tr>
<tr>
<td><code>s.send()</code></td>
<td>#发送TCP数据</td>
</tr>
<tr>
<td><code>s.sendall()</code></td>
<td>#发送TCP数据</td>
</tr>
<tr>
<td><code>s.recvfrom()</code></td>
<td>#接收UDP数据</td>
</tr>
<tr>
<td><code>s.sendto()</code></td>
<td>#发送UDP数据</td>
</tr>
<tr>
<td><code>s.getpeername()</code></td>
<td>#连接到当前套接字的远端的地址</td>
</tr>
<tr>
<td><code>s.getsockname()</code></td>
<td>#当前套接字的地址</td>
</tr>
<tr>
<td><code>s.getsockopt()</code></td>
<td>#返回指定套接字的参数</td>
</tr>
<tr>
<td><code>s.setsockopt()</code></td>
<td>#设置指定套接字的参数</td>
</tr>
<tr>
<td><code>s.close()</code></td>
<td>#关闭套接字，也支持with上下文管理<code>socket.socket()</code></td>
</tr>
</tbody></table>
<h4 id="基于TCP协议的socket"><a href="#基于TCP协议的socket" class="headerlink" title="基于TCP协议的socket"></a>基于TCP协议的socket</h4><h5 id="server端"><a href="#server端" class="headerlink" title="server端"></a>server端</h5><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> socket</span><br><span class="line">sk = socket.socket() <span class="comment">#即socket.socket(socket.AF_INET,socket.SOCK_STREAM)</span></span><br><span class="line">sk.bind((<span class="string">'127.0.0.1'</span>,<span class="number">8898</span>))  <span class="comment">#把地址绑定到套接字</span></span><br><span class="line">sk.listen()          <span class="comment">#监听链接</span></span><br><span class="line">conn,addr = sk.accept() <span class="comment">#接受客户端链接 会和input一样一直等待连接</span></span><br><span class="line">ret = conn.recv(<span class="number">1024</span>)  <span class="comment">#接收客户端信息 会和input一样一直等待着信</span></span><br><span class="line">print(ret)       <span class="comment">#打印客户端信息</span></span><br><span class="line">conn.send(<span class="string">b'hi'</span>)        <span class="comment">#向客户端发送信息</span></span><br><span class="line">conn.close()       <span class="comment">#关闭客户端套接字</span></span><br><span class="line">sk.close()        <span class="comment">#关闭服务器套接字(可选)</span></span><br></pre></td></tr></table></figure>

<h5 id="client端"><a href="#client端" class="headerlink" title="client端"></a>client端</h5><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> socket</span><br><span class="line">sk = socket.socket() <span class="comment"># 创建客户套接字</span></span><br><span class="line">sk.connect((<span class="string">'127.0.0.1'</span>,<span class="number">8898</span>))    <span class="comment"># 尝试连接服务器</span></span><br><span class="line">sk.send(<span class="string">b'hello!'</span>)</span><br><span class="line">ret = sk.recv(<span class="number">1024</span>)         <span class="comment"># 对话(发送/接收)</span></span><br><span class="line">print(ret)</span><br><span class="line">sk.close()            <span class="comment"># 关闭客户套接字</span></span><br></pre></td></tr></table></figure>

<h4 id="常见报错"><a href="#常见报错" class="headerlink" title="常见报错"></a>常见报错</h4><p>Traceback(most recent call last):</p>
<p>OSError: [Error 48] Address already in use</p>
<p>解决方法： 加入一条socket配置，重用ip和端口</p>
<figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> socket</span><br><span class="line"><span class="keyword">from</span> socket <span class="keyword">import</span> SOL_SOCKET,SO_REUSEADDR</span><br><span class="line">sk = socket.socket()</span><br><span class="line">sk.setsockopt(SOL_SOCKET,SO_REUSEADDR,<span class="number">1</span>) <span class="comment">#就是它，在bind前加</span></span><br><span class="line">sk.bind((<span class="string">'127.0.0.1'</span>,<span class="number">8898</span>))</span><br><span class="line">sk.listen()</span><br></pre></td></tr></table></figure>

<p>Traceback(most recent call last):</p>
<p>ConnectionRefusedError: [WinError 10061] 由于目标计算机积极拒绝，无法连接。</p>
<p>解决方法： 修改防火墙设置或者换一个端口号</p>
<h4 id="基于UDP协议的socket"><a href="#基于UDP协议的socket" class="headerlink" title="基于UDP协议的socket"></a>基于UDP协议的socket</h4><p>udp无需监听和建立连接。</p>
<p>udp收发消息会分别接收和发送对方的地址（addr）。</p>
<h5 id="server端-1"><a href="#server端-1" class="headerlink" title="server端"></a>server端</h5><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> socket</span><br><span class="line">udp_sk = socket.socket(type=socket.SOCK_DGRAM)   <span class="comment">#创建一个服务器的套接字</span></span><br><span class="line">udp_sk.bind((<span class="string">'127.0.0.1'</span>,<span class="number">9000</span>))        <span class="comment">#绑定服务器套接字</span></span><br><span class="line">msg,addr = udp_sk.recvfrom(<span class="number">1024</span>)</span><br><span class="line">print(msg)</span><br><span class="line">udp_sk.sendto(<span class="string">b'hi'</span>,addr)                 <span class="comment"># 对话(接收与发送)</span></span><br><span class="line">udp_sk.close()                         <span class="comment"># 关闭服务器套接字</span></span><br></pre></td></tr></table></figure>

<h5 id="client端-1"><a href="#client端-1" class="headerlink" title="client端"></a>client端</h5><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> socket</span><br><span class="line">ip_port=(<span class="string">'127.0.0.1'</span>,<span class="number">9000</span>)</span><br><span class="line">udp_sk=socket.socket(type=socket.SOCK_DGRAM)</span><br><span class="line">udp_sk.sendto(<span class="string">b'hello'</span>,ip_port)</span><br><span class="line">back_msg,addr=udp_sk.recvfrom(<span class="number">1024</span>)</span><br><span class="line">print(back_msg.decode(<span class="string">'utf-8'</span>),addr)</span><br></pre></td></tr></table></figure>

<h4 id="更多方法介绍"><a href="#更多方法介绍" class="headerlink" title="更多方法介绍"></a>更多方法介绍</h4><ul>
<li><p>面向锁</p>
<table>
<thead>
<tr>
<th><code>s.setblocking()</code></th>
<th>设置套接字的阻塞与非阻塞模式</th>
</tr>
</thead>
<tbody><tr>
<td><code>s.settimeout()</code></td>
<td>设置阻塞套接字操作的超时时间</td>
</tr>
<tr>
<td><code>s.gettimeout()</code></td>
<td>得到阻塞套接字操作的超时时间</td>
</tr>
</tbody></table>
</li>
<li><p>面向文件</p>
<table>
<thead>
<tr>
<th><code>s.fileno()</code></th>
<th>套接字的文件描述符</th>
</tr>
</thead>
<tbody><tr>
<td><code>s.makefile()</code></td>
<td>创建一个与该套接字相关的文件</td>
</tr>
</tbody></table>
</li>
</ul>
<p>官方文档对socket模块下的<code>socket.send()</code>和<code>socket.sendall()</code>解释如下：</p>
<figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br></pre></td><td class="code"><pre><span class="line">socket.send(string[, flags]):</span><br><span class="line"><span class="string">'''Send data to the socket. The socket must be connected to a remote socket.</span></span><br><span class="line"><span class="string">The optional flags argument has the same meaning as for recv() above. </span></span><br><span class="line"><span class="string">Returns the number of bytes sent. </span></span><br><span class="line"><span class="string">Applications are responsible for checking that all data has been sent; </span></span><br><span class="line"><span class="string">if only some of the data was transmitted, </span></span><br><span class="line"><span class="string">the application needs to attempt delivery of the remaining data.</span></span><br><span class="line"><span class="string">send()的返回值是发送的字节数量，这个数量值可能小于要发送的string的字节数，</span></span><br><span class="line"><span class="string">也就是说可能无法发送string中所有的数据。如果有错误则会抛出异常。'''</span></span><br><span class="line">	<span class="keyword">pass</span></span><br><span class="line"></span><br><span class="line">socket.sendall(string[, flags]):</span><br><span class="line"><span class="string">'''Send data to the socket. </span></span><br><span class="line"><span class="string">The socket must be connected to a remote socket. </span></span><br><span class="line"><span class="string">The optional flags argument has the same meaning as for recv() above. </span></span><br><span class="line"><span class="string">Unlike send(), this method continues to send data </span></span><br><span class="line"><span class="string">from string until either all data has been sent or an error occurs. </span></span><br><span class="line"><span class="string">None is returned on success. </span></span><br><span class="line"><span class="string">On error, an exception is raised, </span></span><br><span class="line"><span class="string">and there is no way to determine how much data, </span></span><br><span class="line"><span class="string">if any, was successfully sent.</span></span><br><span class="line"><span class="string">尝试发送string的所有数据，成功则返回None，失败则抛出异常。</span></span><br><span class="line"><span class="string">故，下面两段代码是等价的：'''</span></span><br><span class="line"><span class="comment">#sock.sendall('Hello world\n')</span></span><br><span class="line"><span class="comment">#buffer = 'Hello world\n'</span></span><br><span class="line"><span class="comment">#while buffer:</span></span><br><span class="line"><span class="comment">#    bytes = sock.send(buffer)</span></span><br><span class="line"><span class="comment">#    buffer = buffer[bytes:]</span></span><br><span class="line">	<span class="keyword">pass</span></span><br></pre></td></tr></table></figure>

<h3 id="socketserver模块"><a href="#socketserver模块" class="headerlink" title="socketserver模块"></a>socketserver模块</h3><p><a href="https://docs.python.org/zh-cn/3/library/socketserver.html" target="_blank" rel="noopener"><code>socketserver</code></a>模块使一个server端可以同时和多个client端连接（多线程)</p>
<p>与只使用socket时<code>conn,addr = sk.accept()</code>相同的是<br>继承<code>socketserver.BaseRequestHandler</code>之后<br><code>self.request</code> 就相当于conn<br><code>self.client_address</code> 就相当于addr</p>
<h4 id="server端-2"><a href="#server端-2" class="headerlink" title="server端"></a>server端</h4><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> socketserver</span><br><span class="line"></span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Myserver</span><span class="params">(socketserver.BaseRequestHandler)</span>:</span></span><br><span class="line">    <span class="function"><span class="keyword">def</span> <span class="title">handle</span><span class="params">(self)</span>:</span></span><br><span class="line">        self.data = self.request.recv(<span class="number">1024</span>).strip()</span><br><span class="line">        print(<span class="string">"&#123;&#125; wrote:"</span>.format(self.client_address[<span class="number">0</span>]))</span><br><span class="line">        print(self.data)</span><br><span class="line">        self.request.sendall(self.data.upper())</span><br><span class="line"></span><br><span class="line"><span class="keyword">if</span> __name__ == <span class="string">"__main__"</span>:</span><br><span class="line">    HOST, PORT = <span class="string">"127.0.0.1"</span>, <span class="number">9999</span></span><br><span class="line">    <span class="comment"># 设置allow_reuse_address允许服务器重用地址</span></span><br><span class="line">    socketserver.TCPServer.allow_reuse_address = <span class="literal">True</span></span><br><span class="line">    <span class="comment"># 创建一个server, 将服务地址绑定到127.0.0.1:9999</span></span><br><span class="line">    server = socketserver.TCPServer((HOST, PORT),Myserver)</span><br><span class="line">    <span class="comment"># 让server永远运行下去，除非强制停止程序</span></span><br><span class="line">    server.serve_forever()</span><br></pre></td></tr></table></figure>

<h4 id="client端-2"><a href="#client端-2" class="headerlink" title="client端"></a>client端</h4><p>就是最前面的基于TCP的套接字的C端，这里使用with上下文管理的写法</p>
<figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> socket</span><br><span class="line"></span><br><span class="line">HOST, PORT = <span class="string">"127.0.0.1"</span>, <span class="number">9999</span></span><br><span class="line">data = <span class="string">"hello"</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">with</span> socket.socket(socket.AF_INET, socket.SOCK_STREAM) <span class="keyword">as</span> sock:</span><br><span class="line">    sock.connect((HOST, PORT))</span><br><span class="line">    sock.sendall(bytes(data + <span class="string">"\n"</span>, <span class="string">"utf-8"</span>))</span><br><span class="line">    received = str(sock.recv(<span class="number">1024</span>), <span class="string">"utf-8"</span>)</span><br><span class="line"></span><br><span class="line">print(<span class="string">"Sent:     &#123;&#125;"</span>.format(data))</span><br><span class="line">print(<span class="string">"Received: &#123;&#125;"</span>.format(received))</span><br></pre></td></tr></table></figure>

<h3 id="黏包"><a href="#黏包" class="headerlink" title="黏包"></a>黏包</h3><p>现象 : 同时执行多条命令之后，得到的结果很可能只有一部分，在执行其他命令的时候又接收到之前执行的另外一部分结果，这种显现就是黏包。</p>
<h4 id="黏包成因"><a href="#黏包成因" class="headerlink" title="黏包成因"></a>黏包成因</h4><ul>
<li>TCP协议的拆包机制<br>当发送端缓冲区的长度大于网卡的MTU时TCP会将这次发送的数据拆成几个数据包发送出去。</li>
<li>面向流的通信特点和Nagle算法<br>Nagle算法优化后将多次间隔较小且数据量小的数据，合并成一个大的数据块，然后进行封包。</li>
</ul>
<p><img src="" alt="img"></p>
<h4 id="解决方案"><a href="#解决方案" class="headerlink" title="解决方案"></a>解决方案</h4><p>思路：制作报头，提前让接收端知晓自己将要发送的字节流总大小</p>
<p>让发送端在发送数据前，发送<strong>固定长度</strong>的报头，然后接收端循环接收完所有数据。</p>
<h3 id="struct模块"><a href="#struct模块" class="headerlink" title="struct模块"></a>struct模块</h3><p><a href="https://docs.python.org/zh-cn/3/library/struct.html" target="_blank" rel="noopener"><code>struct</code></a>可以把以下类型转成固定长度的bytes</p>
<table>
<thead>
<tr>
<th>Format</th>
<th>C Type</th>
<th>Python type</th>
<th>Standard size</th>
<th>Notes</th>
</tr>
</thead>
<tbody><tr>
<td>x</td>
<td>pad byte</td>
<td>no value</td>
<td></td>
<td></td>
</tr>
<tr>
<td>c</td>
<td>char</td>
<td>string of length 1</td>
<td>1</td>
<td></td>
</tr>
<tr>
<td>b</td>
<td>signed char</td>
<td>integer</td>
<td>1</td>
<td>(3)</td>
</tr>
<tr>
<td>B</td>
<td>unsigned char</td>
<td>integer</td>
<td>1</td>
<td>(3)</td>
</tr>
<tr>
<td>?</td>
<td>_Bool</td>
<td>bool</td>
<td>1</td>
<td>(1)</td>
</tr>
<tr>
<td>h</td>
<td>short</td>
<td>integer</td>
<td>2</td>
<td>(3)</td>
</tr>
<tr>
<td>H</td>
<td>unsigned short</td>
<td>integer</td>
<td>2</td>
<td>(3)</td>
</tr>
<tr>
<td>i</td>
<td>int</td>
<td>integer</td>
<td>4</td>
<td>(3)</td>
</tr>
<tr>
<td>I</td>
<td>unsigned int</td>
<td>integer</td>
<td>4</td>
<td>(3)</td>
</tr>
<tr>
<td>l</td>
<td>long</td>
<td>integer</td>
<td>4</td>
<td>(3)</td>
</tr>
<tr>
<td>L</td>
<td>unsigned long</td>
<td>integer</td>
<td>4</td>
<td>(3)</td>
</tr>
<tr>
<td>q</td>
<td>long long</td>
<td>integer</td>
<td>8</td>
<td>(2)(3)</td>
</tr>
<tr>
<td>Q</td>
<td>unsigned long long</td>
<td>integer</td>
<td>8</td>
<td>(2)(3)</td>
</tr>
<tr>
<td>f</td>
<td>float</td>
<td>float</td>
<td>4</td>
<td>(4)</td>
</tr>
<tr>
<td>d</td>
<td>double</td>
<td>float</td>
<td>8</td>
<td>(4)</td>
</tr>
<tr>
<td>s</td>
<td>char[]</td>
<td>string</td>
<td></td>
<td></td>
</tr>
<tr>
<td>P</td>
<td>char[]</td>
<td>string</td>
<td></td>
<td></td>
</tr>
<tr>
<td>p</td>
<td>void *</td>
<td>integer</td>
<td></td>
<td>(5)(3)</td>
</tr>
</tbody></table>
<ul>
<li><code>struct.pack()</code></li>
<li><code>struct.unpack()</code></li>
</ul>
<p><code>.pack()</code>和<code>.unpack()</code>的参数一样：</p>
<figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&gt;&gt;&gt; </span>struct.pack(<span class="string">'i'</span>,<span class="number">1111111111111</span>)</span><br><span class="line"></span><br><span class="line">struct.error: <span class="string">'i'</span> format requires <span class="number">-2147483648</span> &lt;= number &lt;= <span class="number">2147483647</span> <span class="comment">#这个是范围</span></span><br></pre></td></tr></table></figure>

<p><code>.unpack()</code>将返回一个元组。</p>
<h5 id="使用struct自制报头"><a href="#使用struct自制报头" class="headerlink" title="使用struct自制报头"></a>使用struct自制报头</h5><p>以远程终端功能（雾）为例：</p>
<p>服务端（自定制报头）</p>
<figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> socket, struct, os, subprocess</span><br><span class="line">s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)</span><br><span class="line">s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, <span class="number">1</span>)</span><br><span class="line">s.bind((<span class="string">'127.0.0.1'</span>, <span class="number">8080</span>))</span><br><span class="line">s.listen()</span><br><span class="line">conn, addr = s.accept()</span><br><span class="line"><span class="keyword">while</span> <span class="number">1</span>:</span><br><span class="line">    cmd = conn.recv(<span class="number">1024</span>)</span><br><span class="line">    cd = cmd.split(<span class="string">b'cd '</span>)</span><br><span class="line">    <span class="keyword">if</span> len(cd) == <span class="number">2</span>:</span><br><span class="line">        os.chdir(str(cd[<span class="number">-1</span>].strip(), <span class="string">'utf-8'</span>))</span><br><span class="line">    print(<span class="string">'cmd: %s'</span> % cmd)</span><br><span class="line">    res = subprocess.Popen(cmd.decode(<span class="string">'utf-8'</span>),</span><br><span class="line">                           shell=<span class="literal">True</span>,</span><br><span class="line">                           stdout=subprocess.PIPE,</span><br><span class="line">                           stderr=subprocess.PIPE)</span><br><span class="line">    back_msg = res.stderr.read() <span class="keyword">or</span> res.stdout.read()</span><br><span class="line">    conn.send(struct.pack(<span class="string">'i'</span>, len(back_msg)))  <span class="comment">#先发报头：back_msg的长度</span></span><br><span class="line">    conn.sendall(back_msg)  <span class="comment">#再发真实的内容</span></span><br><span class="line">conn.close()</span><br><span class="line">s.close()</span><br></pre></td></tr></table></figure>

<p>客户端（自定制报头）</p>
<figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> socket, struct</span><br><span class="line">s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)</span><br><span class="line">res = s.connect_ex((<span class="string">'127.0.0.1'</span>, <span class="number">8080</span>))</span><br><span class="line">res <span class="keyword">and</span> print(res)</span><br><span class="line"><span class="keyword">while</span> <span class="number">1</span>:</span><br><span class="line">    msg = input(<span class="string">'&gt;&gt;&gt; '</span>).strip()</span><br><span class="line">    <span class="keyword">if</span> len(msg) == <span class="number">0</span>: <span class="keyword">continue</span></span><br><span class="line">    <span class="keyword">if</span> msg == <span class="string">':q'</span>: <span class="keyword">break</span></span><br><span class="line">    s.send(msg.encode(<span class="string">'utf-8'</span>))</span><br><span class="line">    data_len = struct.unpack(<span class="string">'i'</span>, s.recv(<span class="number">4</span>))[<span class="number">0</span>]  <span class="comment">#接收报头</span></span><br><span class="line">    now_len = <span class="number">0</span></span><br><span class="line">    all_data = <span class="string">b''</span></span><br><span class="line">    <span class="keyword">while</span> now_len &lt; data_len:</span><br><span class="line">        now_data = s.recv(<span class="number">1024</span>)</span><br><span class="line">        all_data += now_data</span><br><span class="line">        now_len += len(now_data)</span><br><span class="line">    print(all_data.decode(<span class="string">'gbk'</span>))  <span class="comment">#windows默认gbk编码</span></span><br><span class="line">s.close()</span><br></pre></td></tr></table></figure>

<p>自此，黏包问题被完美解决。事实上，应用层的协议（FTP等）本质上就是定制的稍微复杂一点的报头。</p>

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                  [
                      [
                          [0,0,1,1,1,0,0],
                          [0,1,1,0,1,1,0],
                          [1,1,0,0,0,1,1],
                          [1,1,0,0,0,1,1],
                          [1,1,0,0,0,1,1],
                          [1,1,0,0,0,1,1],
                          [1,1,0,0,0,1,1],
                          [1,1,0,0,0,1,1],
                          [0,1,1,0,1,1,0],
                          [0,0,1,1,1,0,0]
                      ],//0
                      [
                          [0,0,0,1,1,0,0],
                          [0,1,1,1,1,0,0],
                          [0,0,0,1,1,0,0],
                          [0,0,0,1,1,0,0],
                          [0,0,0,1,1,0,0],
                          [0,0,0,1,1,0,0],
                          [0,0,0,1,1,0,0],
                          [0,0,0,1,1,0,0],
                          [0,0,0,1,1,0,0],
                          [1,1,1,1,1,1,1]
                      ],//1
                      [
                          [0,1,1,1,1,1,0],
                          [1,1,0,0,0,1,1],
                          [0,0,0,0,0,1,1],
                          [0,0,0,0,1,1,0],
                          [0,0,0,1,1,0,0],
                          [0,0,1,1,0,0,0],
                          [0,1,1,0,0,0,0],
                          [1,1,0,0,0,0,0],
                          [1,1,0,0,0,1,1],
                          [1,1,1,1,1,1,1]
                      ],//2
                      [
                          [1,1,1,1,1,1,1],
                          [0,0,0,0,0,1,1],
                          [0,0,0,0,1,1,0],
                          [0,0,0,1,1,0,0],
                          [0,0,1,1,1,0,0],
                          [0,0,0,0,1,1,0],
                          [0,0,0,0,0,1,1],
                          [0,0,0,0,0,1,1],
                          [1,1,0,0,0,1,1],
                          [0,1,1,1,1,1,0]
                      ],//3
                      [
                          [0,0,0,0,1,1,0],
                          [0,0,0,1,1,1,0],
                          [0,0,1,1,1,1,0],
                          [0,1,1,0,1,1,0],
                          [1,1,0,0,1,1,0],
                          [1,1,1,1,1,1,1],
                          [0,0,0,0,1,1,0],
                          [0,0,0,0,1,1,0],
                          [0,0,0,0,1,1,0],
                          [0,0,0,1,1,1,1]
                      ],//4
                      [
                          [1,1,1,1,1,1,1],
                          [1,1,0,0,0,0,0],
                          [1,1,0,0,0,0,0],
                          [1,1,1,1,1,1,0],
                          [0,0,0,0,0,1,1],
                          [0,0,0,0,0,1,1],
                          [0,0,0,0,0,1,1],
                          [0,0,0,0,0,1,1],
                          [1,1,0,0,0,1,1],
                          [0,1,1,1,1,1,0]
                      ],//5
                      [
                          [0,0,0,0,1,1,0],
                          [0,0,1,1,0,0,0],
                          [0,1,1,0,0,0,0],
                          [1,1,0,0,0,0,0],
                          [1,1,0,1,1,1,0],
                          [1,1,0,0,0,1,1],
                          [1,1,0,0,0,1,1],
                          [1,1,0,0,0,1,1],
                          [1,1,0,0,0,1,1],
                          [0,1,1,1,1,1,0]
                      ],//6
                      [
                          [1,1,1,1,1,1,1],
                          [1,1,0,0,0,1,1],
                          [0,0,0,0,1,1,0],
                          [0,0,0,0,1,1,0],
                          [0,0,0,1,1,0,0],
                          [0,0,0,1,1,0,0],
                          [0,0,1,1,0,0,0],
                          [0,0,1,1,0,0,0],
                          [0,0,1,1,0,0,0],
                          [0,0,1,1,0,0,0]
                      ],//7
                      [
                          [0,1,1,1,1,1,0],
                          [1,1,0,0,0,1,1],
                          [1,1,0,0,0,1,1],
                          [1,1,0,0,0,1,1],
                          [0,1,1,1,1,1,0],
                          [1,1,0,0,0,1,1],
                          [1,1,0,0,0,1,1],
                          [1,1,0,0,0,1,1],
                          [1,1,0,0,0,1,1],
                          [0,1,1,1,1,1,0]
                      ],//8
                      [
                          [0,1,1,1,1,1,0],
                          [1,1,0,0,0,1,1],
                          [1,1,0,0,0,1,1],
                          [1,1,0,0,0,1,1],
                          [0,1,1,1,0,1,1],
                          [0,0,0,0,0,1,1],
                          [0,0,0,0,0,1,1],
                          [0,0,0,0,1,1,0],
                          [0,0,0,1,1,0,0],
                          [0,1,1,0,0,0,0]
                      ],//9
                      [
                          [0,0,0,0],
                          [0,0,0,0],
                          [0,1,1,0],
                          [0,1,1,0],
                          [0,0,0,0],
                          [0,0,0,0],
                          [0,1,1,0],
                          [0,1,1,0],
                          [0,0,0,0],
                          [0,0,0,0]
                      ]//:
                  ];

        function drawDatetime(cxt){
            var nums = [];

            context.fillStyle="#005eac"
            var date = new Date();
            var offsetX = 70, offsetY = 30;
            var hours = date.getHours();
            var num1 = Math.floor(hours/10);
            var num2 = hours%10;
            nums.push({num: num1});
            nums.push({num: num2});
            nums.push({num: 10}); //冒号
            var minutes = date.getMinutes();
            var num1 = Math.floor(minutes/10);
            var num2 = minutes%10;
            nums.push({num: num1});
            nums.push({num: num2});
            nums.push({num: 10}); //冒号
            var seconds = date.getSeconds();
            var num1 = Math.floor(seconds/10);
            var num2 = seconds%10;
            nums.push({num: num1});
            nums.push({num: num2});

            for(var x = 0;x<nums.length;x++){
                nums[x].offsetX = offsetX;
                offsetX = drawSingleNumber(offsetX,offsetY, nums[x].num,cxt);
                //两个数字连一块，应该间隔一些距离
                if(x<nums.length-1){
                    if((nums[x].num!=10) &&(nums[x+1].num!=10)){
                        offsetX+=NUMBER_GAP;
                    }
                }
            }

            //说明这是初始化
            if(currentNums.length ==0){
                currentNums = nums;
            }else{
                //进行比较
                for(var index = 0;index<currentNums.length;index++){
                    if(currentNums[index].num!=nums[index].num){
                        //不一样时，添加彩色小球
                        addBalls(nums[index]);
                        currentNums[index].num=nums[index].num;
                    }
                }
            }
            renderBalls(cxt);
            updateBalls();

            return date;
        }

        function addBalls (item) {
            var num = item.num;
            var numMatrix = digit[num];
            for(var y = 0;y<numMatrix.length;y++){
                for(var x = 0;x<numMatrix[y].length;x++){
                    if(numMatrix[y][x]==1){
                        var ball={
                            offsetX:item.offsetX+RADIUS+RADIUS*2*x,
                            offsetY:30+RADIUS+RADIUS*2*y,
                            color:colors[Math.floor(Math.random()*colors.length)],
                            g:1.5+Math.random(),
                            vx:Math.pow(-1, Math.ceil(Math.random()*10))*4+Math.random(),
                            vy:-5
                        }
                        balls.push(ball);
                    }
                }
            }
        }

        function renderBalls(cxt){
            for(var index = 0;index<balls.length;index++){
                cxt.beginPath();
                cxt.fillStyle=balls[index].color;
                cxt.arc(balls[index].offsetX, balls[index].offsetY, RADIUS, 0, 2*Math.PI);
                cxt.fill();
            }
        }

        function updateBalls () {
            var i =0;
            for(var index = 0;index<balls.length;index++){
                var ball = balls[index];
                ball.offsetX += ball.vx;
                ball.offsetY += ball.vy;
                ball.vy+=ball.g;
                if(ball.offsetY > (WINDOW_HEIGHT-RADIUS)){
                    ball.offsetY= WINDOW_HEIGHT-RADIUS;
                    ball.vy=-ball.vy*u;
                }
                if(ball.offsetX>RADIUS&&ball.offsetX<(WINDOW_WIDTH-RADIUS)){

                    balls[i]=balls[index];
                    i++;
                }
            }
            //去除出边界的球
            for(;i<balls.length;i++){
                balls.pop();
            }
        }
        function drawSingleNumber(offsetX, offsetY, num, cxt){
            var numMatrix = digit[num];
            for(var y = 0;y<numMatrix.length;y++){
                for(var x = 0;x<numMatrix[y].length;x++){
                    if(numMatrix[y][x]==1){
                        cxt.beginPath();
                        cxt.arc(offsetX+RADIUS+RADIUS*2*x,offsetY+RADIUS+RADIUS*2*y,RADIUS,0,2*Math.PI);
                        cxt.fill();
                    }
                }
            }
            cxt.beginPath();
            offsetX += numMatrix[0].length*RADIUS*2;
            return offsetX;
        }

        var canvas = document.getElementById("canvas");
        canvas.width=WINDOW_WIDTH;
        canvas.height=WINDOW_HEIGHT;
        context = canvas.getContext("2d");

        //记录当前绘制的时刻
        var currentDate = new Date();

        setInterval(function(){
            //清空整个Canvas，重新绘制内容
            context.clearRect(0, 0, context.canvas.width, context.canvas.height);
            drawDatetime(context);
        }, 50)
})();
</script>

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